1. Field of the Invention
The present invention relates to a recovery mechanism for removing foreign matter from an ink discharge surface of a recording head, more particularly, to an improved recovery mechanism capable of reliable cleaning of a recording head that can be adjusted.
2. Description of the Related Art
In an ink jet recording system in which recorded images are formed by discharging ink onto a recording medium, an ink discharge means typically incorporates electro-thermal transducers or electro-mechanical transducers to apply discharge pressure to the ink.
In the ink discharge means (also referred to herein as an ink jet head), ink droplets or foreign matter, such as dust containing, for example, paper powder, can become attached to an ink discharge surface having therein ink discharge ports during the discharge of ink in an image recording operation.
Such attached objects may cause ink discharge failure, for example, by varying the direction in which the discharged ink travels, or by entering and thereby clogging the ink discharge ports, thus causing deterioration of the recording characteristics.
Conventionally, such a discharge failure is improved or recovered by wiping the ink discharge surface using an elastic sheet or blade made of a flexible material such as rubber to serve as discharge-recovery means for performing what is known as a wiping operation. Such a blade may be retractable relative to a scanning area scanned with the ink jet head mounted on a carriage so that the blade can protrude into the scanning area of the carriage to wipe the ink discharge surface while the carriage is being scanned. Alternatively, the blade may be brought into abutment with and made to slide against the ink jet head.
FIG. 1 is a perspective view showing the schematic structure of an example of a conventional ink jet apparatus. A carriage 2 carrying an ink jet head 1 is moved back and forth along a slide base 4 and a slide shaft 3 by a driving force of a motor 5, which driving force is transmitted to the carriage 2 via a belt 9.
A recovery unit 10 for recovering from a discharge failure of the ink jet head 1, that is, for recovering ink discharge, is fixed outside an end of a printing surface 1A (recording area) faced by the ink discharge surface of the ink jet head 1. The recovery unit 10 includes a blade 12 for cleaning the discharge surface of the ink jet head 1, and a cap 11 for receiving ink discharged from the discharge port or for protecting the ink jet head 1 when recording is suspended.
FIG. 2 is a schematic perspective view of the recovery unit 10. Reference numeral 13 denotes a recovery unit base constituting an outer shell of the unit. A suction recovery operation is performed on the head by drawing ink from the discharge port of the ink jet head by means of a negative pressure of a pump (not shown) driven when the ink jet head is capped. Capping is performed by a driving motor (not shown), a gear group (not shown) and an eccentric cam (not shown), which are provided at the distal end of the driving motor that move the cap 11 toward or away from the head.
A blade cam 6 is rotated about a shaft 7 by the driving force of the driving motor. Reference numeral 21 denotes a blade base which is slidable in a straight line toward the head 1 along the side surface of the base 13. The blade base 21 is urged in a direction in which it is separated from the head by means of a tension spring 23. A blade lever 29 slides against the blade cam 6, whereby cam-shaped irregularities are transmitted in the form of a reciprocative movement of the blade base 21. The blade 12 is mounted on a distal end of the blade base 21. Between the cap 11 and the blade 12 there is a rubbing member 14 for rubbing the discharge port surface of the ink jet head 1 to remove any substance attached thereto.
The amount of reciprocative movement of the blade 12 is determined by the irregularities of the blade cam 20, that is, the optimum value for the normal recording scanning position of the ink jet head 1 is set. However, in recent years, recording apparatuses have been improved in such a manner that they can perform recording on various types of recording media. When printing is performed on, for example, a sheet of thick paper, the head is moved together with the carriage to account for the thicker recording medium. In such a case, the position of the head relative to the blade will vary, and the amount the blade projects onto the head during cleaning differs between the upper and lower portions of the head, thus affecting the blade's wiping performance.